Vanama Pavan Kumar

Vapor phase selective hydrogenation of acetone to methyl isobutyl ketone (MIBK) over Ni/CeO2 catalysts

Ceria supported nickel oxide catalysts with varying nickel loadings from 1.0 to 20.0 wt% were prepared by the impregnation method. The catalysts were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (UV-DRS), temperature programmed reduction (TPR), temperature programmed desorption (TPD) of CO2, and surface area measurements. The dispersion of nickel and metal area were determined by the hydrogen chemisorption method. The X-ray diffraction patterns suggest the presence of crystalline NiO phase beyond 2.5 wt% of Ni on ceria. The UV-visible diffuse reflectance spectra reveal the presence of two types of nickel species on the CeO2 support. TPR patterns reveal the presence of highly dispersed surface free nickel oxide species at lower temperatures and bulk NiO at higher temperatures. The basicity of the catalysts measured by the CO2 TPD method was found to increase with an increase in nickel loading up to 2.5 wt% and decrease with further increase in nickel loading. The vapor phase condensation and selective hydrogenation of acetone to methyl isobutyl ketone (MIBK) were carried out on Ni/CeO2 catalysts and the catalytic properties are correlated with the results of CO2 TPD measurements and also with the dispersion of the nickel species supported on ceria.

Catalytic performance of Pt/AlPO4 catalysts for selective hydrogenolysis of glycerol to 1,3-propanediol in the vapour phase

Hydrogenolysis of glycerol to 1,3-propanediol was investigated in the vapour phase over a series of Pt/AlPO4 catalysts with platinum loadings ranging from 0.5 to 3 wt%. The catalysts were prepared by a wet impregnation method and characterized by various techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), BET surface area, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and CO-chemisorption methods. Ex situ pyridine adsorbed FTIR analysis and temperature programmed desorption (TPD) of NH3 were employed to investigate the acidic properties of the catalysts. Further, the effect of reaction temperature, hydrogen flow rate, glycerol concentration and various contents of platinum (0.5 to 3 wt%) have been investigated to find the optimum reaction conditions. Superior performance with almost 100% conversion of glycerol and above 35% selectivity to 1,3-propanediol was obtained over 2 wt% Pt/AlPO4 at 260 °C and atmospheric pressure. The influence of acidity of the catalyst and its correlation to the catalytic performance (selectivity and conversion) has been studied. The high strength of weak acidic sites and Bronsted acidity of the catalyst measured by NH3-TPD and Pyr-FTIR were concluded to play a key role in selective formation of 1,3-propanediol. XRD, TEM and CO-chemisorption studies revealed that platinum was well dispersed on AlPO4 which further contributed to higher catalytic activity for glycerol hydrogenolysis.

Vapor Phase Oxidation of Benzyl Alcohol Over Gold Nanoparticles Supported on Mesoporous TiO2

The vapor phase oxidation of benzyl alcohol was investigated over gold nanoparticles supported on mesoporous titanium dioxide (anatase) catalysts under aerobic conditions. The catalysts were prepared by homogeneous deposition–precipitation method using urea as the precipitating agent. The physico-chemical properties of the synthesized catalysts were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), pore size distribution (PSD), CO-chemisorption and X-ray photoelectron spectroscopy (XPS) techniques. The crystallite size of gold in Au/TiO2 catalysts was measured from XRD. The mesoporosity of TiO2 support and Au/TiO2 catalysts were confirmed by PSD analysis. TEM results suggest that gold nanoparticles are well dispersed over mesoporous TiO2. The catalytic functionality is well substantiated with particle size measured from TEM. XPS results reveal the formation of Au(0) after chemical reduction by NaBH4. The vapor phase benzyl alcohol oxidation was used as a test reaction to investigate the influence of the metal, nature of the support, and of metal-support interactions in Au/TiO2 catalysts and also the catalytic activity and stability of the Au/TiO2 catalysts. The conversion of benzyl alcohol was found to increase with decrease in the size of gold particles. Smaller gold particles and a higher amount of small gold particles had a beneficial effect on the catalytic activity. The catalytic activity in the presence of oxygen is believed to be associated with the transport of electrons through the catalyst to the adsorbed oxygen on the surface.Graphical Abstract.

Synthesis and characterization of Cs-exchanged heteropolyacid catalysts functionalized with Sn for carbonolysis of glycerol to glycerol carbonate

Cs exchanged heteropolyacid catalysts functionalized with various Sn contents were prepared by wet impregnation method. These catalysts were characterized by X-ray diffraction, FT-IR, Raman spectroscopy, temperature programmed desorption of ammonia and BET surface area measurements. The catalytic properties of Sn–CsPW catalysts were evaluated for the synthesis of glycerol carbonate and they exhibit an unprecedented activity for the higher glycerol conversion and selectivity towards glycerol carbonate under vacuum conditions. Sn-functionalized Cs exchanged heteropolyacid catalysts (CsPW) play a significant role in the enhancement of acidity, catalytic activity and stability. The glycerol conversion and the selectivity of carbonate formation mainly depend on the Sn content and acidity of the catalysts. Different reaction parameters such as Sn molar ratio, glycerol to urea molar ratio, reaction temperature were investigated and also optimum conditions were established. The catalyst containing molar ratio of 3:1 Sn–CsPW has shown highest conversion and glycerol carbonate selectivity.

Direct Hydrogenolysis of Glycerol to Biopropanols over Metal Phosphate Supported Platinum Catalysts

Several metal phosphate supported platinum catalysts (Pt/AlP, Pt/TiP, Pt/ZrP and Pt/NbP) have been synthesized for the direct hydrogenolysis of glycerol to produce bio-propanols performed under mild reaction conditions. The catalysts were screened for its activity towards production of propanols from glycerol hydrogenolysis and the reaction has been optimized by studying various reaction parameters such as effect of platinum loading, reaction temperature, hydrogen flow rate, glycerol concentration and reaction time. Among the catalysts investigated, 2Pt/TiP presented a remarkable catalytic performance for vapour phase hydrogenolysis of glycerol with 100% conversion of glycerol and 97% selectivity to total propanols (1-propanol + 2-propanol) at 220 °C and atmospheric pressure. The high efficiency of 2Pt/TiP catalyst is probably be due to the strong acidity of catalyst and the uniform dispersion of small Pt particles on surface of TiP that could enable the dehydration-hydrogenation route of glycerol hydrogenolysis. Further, the structural characteristics of used catalyst have been investigated in order to understand the stability of the catalyst. Therefore, a more economical and sustainable approach of producing value added propanols from bio-derived glycerol over highly efficient catalytic system is herein presented.Graphical Abstract